# Perform n steps to convert every digit of a number in the format [count][digit]

Given a number num as a string and a number N. The task is to write a program which converts the given number num to another number after performing N steps. At each step, every digit of num will be written in the format [count][digit] in the new number, where count is the number of times a digit occurs consecutively in num.

Examples:

Input: num = “123”; n = 3
Output: 1321123113
For, n = 1: 123 becomes 1 time 1, 1 time 2, 1 time 3, hence number 111213
For, n = 2: 3 times 1, 1 time 2, 1 time 1, 1 time 3, hence number 31121113
For, n = 3: 1 time 3, 2 times 1, 1 time 2, 3 times 1, 1 time 3, hence number 1321123113

Input: num = “1213”; n = 1
Output: 11121113

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: Parse the string’s characters as a single digit and maintain a count for that digit till a different digit is found. Once a different digit is found, add the count of the digit to the new string and number to it. Once the string is parsed completely, recur for the function again with this new string till n steps are done.

Below is the implementation of the above approach:

## C++

 // C++ program to convert number // to the format [count][digit] at every step #include using namespace std;    // Function to perform every step void countDigits(string st, int n) {        // perform N steps     if (n > 0) {         int cnt = 1, i;         string st2 = "";            // Traverse in the string         for (i = 1; i < st.length(); i++) {             if (st[i] == st[i - 1])                 cnt++;             else {                 st2 += ('0' + cnt);                 st2 += st[i - 1];                 cnt = 1;             }         }            // for last digit         st2 += ('0' + cnt);         st2 += st[i - 1];            // recur for current string         countDigits(st2, --n);     }        else         cout << st; }    // Driver Code int main() {        string num = "123";     int n = 3;        countDigits(num, n);        return 0; }

## Java

 // Java program to convert number  // to the format [count][digit] at every step class GFG  {        // Function to perform every step     public static void countDigits(String st, int n)     {            // perform N steps         if (n > 0)          {             int cnt = 1, i;             String st2 = "";                // Traverse in the string             for (i = 1; i < st.length(); i++)              {                 if (st.charAt(i) == st.charAt(i - 1))                     cnt++;                 else                 {                     st2 += ((char) 0 + (char) cnt);                     st2 += st.charAt(i - 1);                     cnt = 1;                 }             }                // for last digit             st2 += ((char) 0 + (char) cnt);             st2 += st.charAt(i - 1);                // recur for current string             countDigits(st2, --n);         }          else             System.out.print(st);     }        // Driver Code     public static void main(String[] args)      {         String num = "123";         int n = 3;         countDigits(num, n);     } }    // This code is contributed by // sanjeev2552

## C#

 // C# program to convert number  // to the format [count][digit] at every step using System; class GFG  {    // Function to perform every step public static void countDigits(string st, int n) {        // perform N steps     if (n > 0)      {         int cnt = 1, i;         string st2 = "";            // Traverse in the string         for (i = 1; i < st.Length; i++)          {             if (st[(i)] == st[(i - 1)])                 cnt++;             else             {                 st2 += ((char) 0 + (char) cnt);                 st2 += st[(i - 1)];                 cnt = 1;             }         }            // for last digit         st2 += ((char) 0 + (char) cnt);         st2 += st[(i - 1)];            // recur for current string         countDigits(st2, --n);     }      else         Console.Write(st); }    // Driver Code public static void Main()  {     string num = "123";     int n = 3;     countDigits(num, n); } }    // This code is contributed by // Code_Mech.

Output:

1321123113

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Improved By : sanjeev2552, Code_Mech

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